A resistor paste is generally mainly comprised of a glass material, conductive materials, and an organic vehicle (binder and solvent). The glass material is included in the resistor paste for adjusting the resistance value and for imparting bondability to the substrate etc. The resistor paste is printed on a substrate, then fired to form a thick film (5 to 25 μm) resistor.
Most conventional resistor pastes include lead oxide-based glass as the glass material and contain ruthenium oxide or a compound of the ruthenium oxide and lead as a conductive material and therefore are lead-containing pastes.
However, use of a lead-containing resistor paste is not desirable from the viewpoint of environmental pollution, so various proposals have been made regarding lead-free thick film resistor pastes (for example, see the following shown Patent Document 1, Patent Document 2, and Patent Document 3).
Normally, in thick film resistors, even if formed by the same conditions (printing and firing conditions), the characteristics (resistance value, TCR (temperature coefficient of resistance), reliability characteristic, etc.) will not match due to the substrate used. To obtain the necessary characteristics, it is sufficient to use resistors developed for the individual substrates.
As the reason why the characteristics are not constant due to the substrate used, generally the difference in the linear heat expansion coefficients of the substrates is discussed. However, when using a dielectric substrate having BaTiO3 as a main ingredient as with chip capacitor devices, isolator devices, etc., the dielectric substrate and resistor react in the firing process. As a result, there is the problem that the resistance value rises and the TCR and reliability characteristic deteriorate (for example, see Patent Document 4). In particular, obtaining the desired characteristics in a resistor having a low resistance value of about 10 to 300 Ω/□ was extremely difficult.
Patent Document 1 Japanese Patent Publication (A) No. 8-253342
Patent Document 2 Japanese Patent Publication (A) No. 10-224004
Patent Document 3 Japanese Patent Publication (A) No. 11-251105
Patent Document 4 Japanese Patent Publication (A) No. 60-92601